DEFRA Consultation on Improving Biodiversity Net Gain Implementation for Minor, Medium & Brownfield Development

Since April 2024, the Environment Act 2021 has required developments to achieve a 10% biodiversity net gain, meaning, a development will result in a more or better quality natural habitat than there was before the development. However, stakeholders have flagged implementation challenges for smaller sites, particularly in relation to costs, complexity, and habitat availability.

The Department for Environment, Food & Rural Affairs (DEFRA) has recently launched an eight‑week consultation aimed at improving the delivery of Biodiversity Net Gain (BNG) in minor, medium-sized, and brownfield developments across England. The consultation runs until 24 July 2025 and seeks stakeholder feedback regarding the implementation of the BNG framework to inform potential changes to BNG regulations and guidance.

The consultation can be viewed here: https://consult.defra.gov.uk/defra-biodiversity-net-gain/improving-the-implementation-of-biodiversity-net-g/

Improving Exemptions

The Environment Act includes a short list of developments which are exempt from meeting BNG requirements such as householder applications, developments which do not impact priority habitats and developments that impact less than 25 sqm of onsite area habitat. The consultation is considering new exemptions for certain types of development such as temporary planning permissions and all ‘minor’ developments.

Streamlining the BNG Metric Process

The statutory biodiversity metric is used to measure biodiversity losses and gains from a development, which is shown as ‘biodiversity units’. The consultation seeks to rename the “small sites metric” to a more user-friendly “low impact metric,” allowing it for medium-sized projects, simplifying trading rules, combining habitat categories, and moving to a more user-friendly digital tool.

Increasing flexibility for Off-Site Gains

The Biodiversity Gain hierarchy, requires developers to deliver onsite habitat improvements in the first instance, followed by off-site gains and finally by purchasing statutory credits from the government as a last resort. The consultation seeks to relax the hierarchy to place onsite habitat improvements with the same preference as off-site, for minor development only. This would make it easier for small sites to discharge the statutory BNG condition and removes the need to evidence to LPA’s that all on-site possibilities had been exhausted.

Brownfield Developments with Open Mosaic Habitat  

Open Mosaic Habitat (OMH) is a type of priority habitat which predominantly exists on previously disturbed brownfield sites. It is not always possible or viable for brownfield developments to create and enhance OMH on-site due to spatial constraints. Therefore, DEFRA are considering updating the metric definitions for OMH to support ecologists in the identification of OMH and allowing the loss of OMH to be compensated with an alternative habitat mosaic with similar ecological benefits.

Next Steps

Once the consultation concludes, DEFRA will review and publish the responses received alongside a government response to the consultation. Changes to guidance, the metric tool, and regulations are expected to follow but, in the meantime, existing BNG mandates continue to remain active and developers must continue to meet the 10% biodiversity gain requirement using the current system.

Article prepared by: Joshua Hindle & Raveen Bhamra
Contact: info@firstplan.co.uk